如何为socket.on（）传递更多参数

Question

For socket.on("someChannel", handler), I hope to extract out my handler function to another file. As such, they need to be passed in the socket obj and some more additional info.

Like:

socket.on("myEvt", myEvtHandler);

myEvtHandler(socket, additionalInfo, data) {//some stuff here}

But I can't. The best I can think of is to do closure:

(function(socket, addtionalInfo) {
    socket.on("myEvt", function(data) {
        myEvtHandler(socket, addtionalInfo, data);
    });
})(socket, addtionalInfo);

Is this correct? Are there better ways?

Answer 1

You can create a partial function using bind :

socket.on("myEvt", myEvtHandler.bind(null, socket, additionalInfo));

The bind() will return a function with the first two arguments already 'filled in'. The first argument passed to bind() ( null in this case) is going to be the this object in your handler ( more info ).

Any additional arguments passed by socket.io to the handler will be available from the third argument onwards:

function myEvtHandler(socket, additionalInfo, data) { ... }

Similarly, this would do (almost) the same:

socket.on("myEvt", function(data) {
  myEvtHandler(socket, additionalInfo, data);
});